Ellipse drafting instrument



Sept.

Filed May 9, 1955 J. B. SHAW 2 Sheets-Sheet 1 Fig. .2. 30 28 22 26 as f i j} v 7 32 F /8 33 4 36 7 JOHN B. SHA w BY mbhwl ATTORNEY Sept. 11, 1956 J. B. SHAW 2,762,126

ELLIPSE DRAFTING INSTRUMENT Filed May 9, 1955 2 Sheets-Sheet 2 Jar/g3, 50

22 28 43 F 5 5 30 20 /5 ll 1 36 //Z/ V3 V5 24 23 29 35 V6 V5 A l 24 I I 27 c D INVENTOR. JOHN BSHAW BY m g M ATTORNEY United States Patent C ELLIPSE DRAFTING INSTRUMENT John B. Shaw, Los Angeles, Calif.

Application May 9, 1955, Serial No. 507,077

2 Claims. (Cl. 33-31) My invention relates generally to trammels and more particularly to instruments for scribing or drawing ellipses.

An object of my invention is to provide an ellipse drafting instrument which is characterized by its simplicity of construction and ease of operation to accurately scribe ellipses of any desired proportions of major and minor axes in accordance with suitable adjustments of the instrument which can be made with the utmost ease and dispatch.

Another object of my invention is to provide an ellipse drafting instrument which is compact and rugged in construction and which is composed of simply constructed and assembled parts enabling the instrument to be inexpensively manufactured so as to place it within a price range which will promote maximum sale of the instrument among those who would have use therefor for many different purposes in the arts and trades.

With these and other objects in view, my invention resides in the combinations, arrangements and functional relationships of elements as set forth in the following specification and particularly pointed out in the appended claims.

In the accompanying drawings,

Figure l is a view showing in plan, one form of ellipse drafting instrument embodying my invention;

Figure 2 is a vertical sectional view taken on the line 22 of Figure 1;

Figure 3 is a vertical sectional view taken on the line 33 of Figure 1;

Figure 4 is an enlarged fragmentary sectional view taken on the line 4-4 of Figure 2;

Figure 5 is an enlarged fragmentary sectional view taken on the line 55 of Figure 3; and

Figure 6 is a plan view of a chart which may be used as a guide in adjusting the instrument to scribe ellipses of predetermined proportions.

Referring specifically to the drawings, my invention comprises a support in the form of a rectangular frame F which may be constructed of metal, plastic or other suitable material to provide one pair of parallel, spaced track or guide members 10 and a second pair of parallel, spaced track or guide members 11. The members 10 and 11 are rigidly secured at their ends in exactly right angular relation by rivets 12, with the members of one pair laterally offset from those of the other pair as clearly shown in Figures 2 and 3.

Sharply pointed pins 13 project laterally from the corners of the frame F and are adapted to be pressed into the surface of a drawing board or other support to temporarily secure the frame in a selected fixed position for the drawing of an ellipse or ellipses as desired. The

confronting edges of the members 10 are grooved to 4 provide guideways 15 in which are received the edges or peripheral portions of a minor axis controlling disk or circular element 16, whereas the confronting edges of the members 11 are similarly grooved to provide guideways 17 in which are received the edges or peripheral portions of a major axis controlling disk or circular element 13, all as clearly shown in Figures 1, 2 and 3.

Projecting from the disk 16 at one side of the center thereof is a pin or spline 20 which works in a slot 21 in the disk 18, whereas at the opposite side of the center of the disk 16 a clamping screw'22 having a head 23 is provided with a square shank portion 24 which is fitted in a similarly shaped opening in the disk 16. The screw 22 projects through a slot 25 in the disk 18 which is parallel to the slot 21.

The portion 24 of the screw 22 receives a pointer 26 (Figure 5) adapted to co-act with a scale 27 on the disk 18 which bears indicia in the form of capital letters A, B, C, D, E, F and G associated with uniformly spaced graduations of the scale, all for a purpose to be later described. From the portion 24 the screw 22 is reduced in diameter and threaded to receive a thumb nut 28, and between the disks 16 and 18 a filler washer 29 is mounted on the screw, all so that upon loosening the nut, the disks will be free for relative adjustment radially from a concentric relationship to any eccentric relationship to a predetermined maximum, it being clear that the pin 20 and screw 22 co-act to confine the disks to relative radial adjustment and to compel rotation of the disks as a unit when clamped by the nut 28 in any selected position of adjustment.

A support in the form of an arm 30 is provided with spaced bearings 31 receiving a pin 32 mounted in a bearing 33 on the disk 13 to mount the arm diametrically of the disk and parallel to the lengths of the slots 26 and 25 for pivotal movement laterally of the disk. A scriber 35 which may be a pencil or any other form of marker, cutter or groover, is mounted in a barrel 36 having an externally threaded shank 37 which projects through a longitudinal slot 38 in the arm 30 and is milled at opposite sides to provide fiat surfaces 39 which are non-rotatably received in the slot.

A pointer 40 is provided with an opening 41 nonrotatably receiving the shank 37 as shown in Figure 4 and co-acting with a scale 42 on the arm 30 which bears indicia in the form of numerals 1, 2, 3, 4, 5, and 6 associated with uniformly spaced graduations of the scale, for use in conjunction with the scale 27 and with a chart C ,(Figure 6) in a manner to be later described. A knurled nut 43 is threaded on the shank 37 to clamp the pencil 35 in any selected position of adjustment in the slot 38 from a position at the center of the disk 18 to one of maximum eccentricity as determined by the length of the slot.

The pencil 35 projects freely through relatively large sight openings 45 and 46 in the disks 16 and 13 for engagement with a surface such as a sheet of paper 47 on a drawing board 43 on which an ellipse is to be scribed. A finger piece in the form of a knob 50 is provided on the free end of the arm 30 by which the disks 16 and 18 may be rotated as a unit to scribe the ellipse on the surface in the operation of the invention which is as follows:

Let it be assumed that it is described to scribe an ellipse the major axis of which is 5 /2 inches and the minor axis 2% inches, and that the scales 27 and 42 are graduated in inches and fractions thereof. The pencil 35 is first adjusted along the slot 38 for the pointer 40 to be opposite the 5 /2 inch graduation on the scale 42, and is then clamped in fixed position by the nut 43. In this position of adjustment the scriber 35 will be located eccentrically of the center of the disk 18 a distance of 2% inches, or one half the major axis.

The position of adjustment of the pointer 26 with reference to the scale 27 to eccentrically relate the disks 316 and 18 the exact amount necessary to obtain the minor axis of 2% inches may be accomplished by exboard 48 and fix the instrument in position.

perimentally adjusting the pointer 26 and then drawing an ellipse which is then measured to determine the error, if any, followed by one or more readjustments and drawing of ellipses until the correct size is obtained.

However, in orderto expedite the correct setting of the pointer 26 to obtain the 2 /2 inch minor axis, the chart C may he used. This chart is scaled and graduated in inches and fractions thereof both horizontally and vertically to provide a pattern of perfect squares made up of intersecting vertical and horizontal lines 55 and 56, respectively, the lines 55 representing the major axis scale and the lines 56 the minor axis scale. Oblique lines 57 extend diagonally of the chart and intersect the lines 55-56 at their intersections, the lines 57 having the indicia A, B, C, D and etc., corresponding to the scale 27 of the disk 18, starting with A to designate that one of the lines 57 extending from the common of the major and minor scales on the chart.

By noting the point of intersection of that one of the lines 55 representing 5 /2 inches, or the major axis, and that one of the lines 56 representing 2 inches, or the minor axis, it will be seen that this intersection is on the D line 57 on the chart, thus indicating that the pointer 26 should be correspondingly adjusted on the scale or the disk 18 to obtain the minor axis ofZ /Zinches.

With the instrument thus adjusted and placed'on the drawing 47 at the desired location, the frame F is pressed downwardly to cause the pins 13 topenetrate the drawing By now grasping the knob 59 to press the pencil in contact with the paper 47, and then imparting force to the knob 56 in a direction to rotate the disks as a unit, the disks will co-act with the respective guideways 15 and 17 by bodily shifting the positions of the disks therein in accordance with the eccentric relationship of the disks and the eccentric position of the pencil, to the end that the latter will scribe an ellipse of the desired-proportion on the paper.

I claim:

1. An ellipse drafting instrument comprising: a pair of circular elements, one for controlling the major axis of an ellipse and the other the minor axis thereof; means co-acting with peripheral portions of said elements to mount same, respectively, for movement in rectilinear paths at right angles to each other while rendering the elements free to rotate; one of said elements having parallel slots therethrough at opposite sides of its center; the other element having a pin working in one of said slots; said other element having a clamp screw working in the other of said slots for co-action with said pin in operatively connecting the elements for rotation as a unit and for relative adjustment to occupy various eccentric positions; a nut threaded on said screw for co-action therewith in clamping said elements in any selectedposition of adjustment; said elements having openings therethrough; an arm pivotally mounted on said one of the elements and having a longitudinal slot; a scriber having a screw threaded shank and being mounted in said slot for adjustment to occupy variouseccentric positions with respect to the center of said one element and to project through said openings; a knob on said arm by which the scriber may be pressed into engagement with a surface and rotational movement imparted to said elements to scribe an ellipse on the surface in accordance with the relative fitCSlZIiCllZY of the elements and the eccentric position of the scriber on said'arm; and a nut on said shank of the scriber for clamping the latter in any adjusted position.

2. An ellipse drafting instrument comprising; a rectangular frame having pairs of spaced guideways, with,

the guideways of each pair in confronting relation and extending at right angles to the guideways of the other H other disk having a pin working in one of said slots; said other disl; having a clamp screw working in the other of said slots for co-action with said pin in operatively connecting the disks for rotation as a unit and for relative adjustment to occupy various eccentric positions; a nut threaded on said screw for co-action therewith in securing said disks in adjusted position; said disks having sight openings therethrough; an arm pivotally mounted on said one of the disks and having a longitudinal slot; a scriber adjustably mounted in said slotto occupy various eccentric positions with respect to the center of said one disk and to project through said openings into engagement with a surface to scribe an ellipse thereon in accordance with the eccentric adjustments of said disks and scriber;

and a finger piece on said arm by which the scriber may be pressed into scribing engagement with the surface and the disks rotated.

References Cited in the file of this patent UNITED STATES PATENTS 

